Early-Stage Detection of Solid Oxide Cells Anode Degradation by Operando Impedance Analysis

Solid oxide cells represent one of the most efficient and promising electrochemical tech- nologies for hydrogen energy conversion. Understanding and monitoring degradation is essential for their full development and wide diffusion. Techniques based on electrochemical impedance spectroscopy and distribution of relaxation times of physicochemical processes occurring in solid oxide cells have attracted interest for the operando diagnosis of degradation. This research paper aims to validate the methodology developed by the authors in a previous paper, showing how such a diagnostic tool may be practically implemented. The validation methodology is based on applying an a priori known stress agent to a solid oxide cell operated in laboratory conditions and on the discrete measurement and deconvolution of electrochemical impedance spectra. Finally, experi- mental evidence obtained from a fully operando approach was counterchecked through ex-post material characterization

Operando Analysis of Losses in Commercial-Sized Solid Oxide Cells: Methodology Development and Validation

The development of decarbonised systems is being fostered by the increasing demand for technological solutions for the energy transition. Solid Oxide Cells are high-efficiency energy conversion systems that are foreseen for commercial development. They exhibit potential power generation and power-to-gas applications, including a reversible operation mode. Long-lasting high performance is essential for guaranteeing the success of the technology; therefore, it is fundamental to provide diagnosis tools at this early stage of development. In this context, operando analysis techniques help detect and identify incipient degradation phenomena to either counteract damage at its origin or correct operando protocols. Frequent switches from the fuel cell to the electrolyser mode add more challenges with respect to durable performance, and deep knowledge of reverse- operation-induced damage is lacking in the scientific and technical literature. Following on from preliminary experience with button cells, in this paper, the authors aim to transfer the methodology to commercial-sized Solid Oxide Cells. On the basis of the experimental evidence collected on planar square cells under dry and wet reactant feed gases, the main contributions to impedance are identified as being charge transfer (f = 103–104 Hz), oxygen surface exchanged and diffusion in bulk LSCF (f = 102–103 Hz), and gas diffusion in the fuel electrode (two peaks, f = 1–100 Hz). The results are validated using the ECM methodology, implementing an LRel(RctQ)GWFLW circuit

IMECE2002-33191 PERFORMANCE IMPROVEMENT OF AN INDUSTRIAL CHILLER THROUGH THE OPTIMIZATION OF THE CONTROL LOGIC

ABSTRACT According to the tasks agreed within the Kyoto protocol, in terms of CO 2 emissions reduction, the European Community is promoting energy saving. The introduction of energetic classification for electrical household appliances, makes consumption as a parameter of choice for consumers and thus represents a relevant tool for the promotion of energy saving. Therefore the interest in the evaluation and minimization of electric consumption for industrial appliances is also evident. The aim of the present study is to investigate alternative control solutions to improve the performance and diminish the energy consumption of an industrial chiller. This was carried out through software modeling of the system and experimental validation of the best performing solutions. Simulated trends show good agreement with experimental data and allow the definition of a suitable PID controller that performs good temperature regulation while slightly reducing energy demand. Further ameliorations were considered and preliminary results are shown both for optimal control and neural modeling of the chiller. Results obtained encourage to continue in the development of better performing regulators, also through neuro -fuzzy logic control

IMECE 2004-60096 DEVELOPMENT OF AN INNOVATIVE DEFROSTING SYSTEM FOR COMMERCIAL CHILLER EVAPORATORS THROUGH PIEZOELECTRIC ELEMENTS APPLICATION

ABSTRACT The present study relates to the design of an innovative defrosting system for commercial chiller evaporators. This system is based on piezoelectric plates connected to the evaporator fins and driven at ultrasonic frequencies by a suitable electronic circuit. The operational frequency of piezoelectric elements is chosen to be close to the first harmonics of the fin resonance frequency in the ultrasonic range. The electronic driving system supplies the electric voltage required at the operational frequency starting from the PVM 0-5V signal output of a microcontroller. Moreover, the measurement of the absorbed current is acquired by the microcontroller as feedback to tune the operational frequency at the variation of the fin mass due to frost deposit and detachment. Experimental results show that the approach inhibits the frost deposit during chiller operation, increasing the period between two consecutive defrosting phases which currently is typically no greater than 6 hours. This is an important result considering that while defrosting the chiller must be shut off, depending on the defrosting methods applied, with negative effects on the goods being preserved. The system was developed in collaboration of ISA S.p.A and patente

Aluminum Steam Oxidation in the Framework of Long‐Term Energy Storage: Experimental Analysis of the Reaction Parameters Effect on Metal Conversion Rate

Aluminum is a promising material as an alternative green energy carrier thanks to its very high volumetric energy density and full recyclability. Aluminum oxidation with steam in the temperature range of 600–900 °C is investigated as an innovative and promising methodology for aluminum conversion resulting in hydrogen and heat production. Reaction times, hydrogen production rate and yield are assessed varying operational parameters such as temperature, steam to aluminum ratio, and gas hourly space velocity within the reactor. The conversion yield of aluminum is assessed at 73.13% at 900 °C and ambient pressure, with reaction times comparable with the one reported in the literature for water oxidation in batch-pressurized reactors. Moreover, over 750 °C, alumina is produced in microparticles, allowing reactor operating times up to 1 h without incurring in the clogging effect. The obtained results are promising for the continuous operating condition of a future full-scale reactor

Hybrid Energy Storage and Hydrogen Supply Based on Aluminum—a Multiservice Case for Electric Mobility and Energy Storage Services

The realization of a fully decarbonized mobility and energy system requires the availability of carbon-free electricity and fuels which can be ensured only by cost-efficient and sustainable energy storage technologies. In line with this demand, a techno-economic evaluation of aluminum as a cross-sectoral renewable energy carrier is conducted. The assessment, based on a newly developed process, involves the wet combustion of Aluminum at 700 degrees C resulting in heat and hydrogen (H-2) generation. The designed conversion plant enables the contemporaneous generation of electricity and on demand H-2 (up to 4 MW and 46.8 kg h(-1)) with round-trip efficiencies as high as 40.7% and full recycling of the Al2O3 waste. This study, assuming the carbon-free production of Al and three different energy cost scenarios, proves the feasibility of the e-fueling station business case. The overall energy conversion including fuel production (power-to-Al), utilization (Al-to-power and Al-to-H-2), and recycling requires a capital investment of 5200 euro per kW installed power without additional primary material demand. Hence, the estimated power-to-X cost for the Al-based H-2 is estimated in the range of 4.2-9.6 euro kg(-1) H-2, while wind and solar power based green H-2 production cost varies from 6.5 to 12.1 euro kg(-1) H-2

Na-seawater battery technology integration with renewable energies: The case study of Sardinia Island

Europe has committed to net zero carbon dioxide emissions by 2050 to boost the clean energy transition. Renewable electricity will be the key energy medium for decarbonization and a huge increase in renewable energy sources (RES) exploitation is expected. Due to RES stochastic character, an extensive energy storage integration in the energy system is needed to avoid the mismatch between generation and demand profiles. Reactive metals are promising energy carriers and storage media characterized by high volumetric energy densities and circularity, due to ease of storage and transportation, material availability and low cost. Among them, sodium is a largely available element since it can be extracted from seawater and exploited through the innovative sodium-seawater battery (SWB). Sodium cations are transferred from SWB’s open cathode to the anode side during charging. Upon discharge, Na metal is oxidized to Na$^+$ ions, which are discarded in seawater. This study assesses the impact of SWB technology focusing on Sardinia Island as a case study. For short-term application, SWB integration to wave energy converters allows a potential reduction of greater than 85% of generated power fluctuations, largely improving the quality of power injected into the grid. Regarding the long-term scenario, SWBs implementation in the energy system allows coverage of the Sardinia annual energy demand thanks to the integration of ∼340,000 cubic meter of Na metal, corresponding to a 12-m height Na reservoir under 4 soccer fields. SWB application to Sardinia also produces CO$_2$ sequestration while covering ∼29% of desalinated water requirements for the Sardinian population

Real time power management strategy for hybrid energy storage systems coupled with variable energy sources in power smoothing applications

Abstract As the renewable energy sources (RES) production is strongly influenced by multiple geographic factors and highly variable, the need for both energy storage integration and robust real-time power management strategies development is obvious. Wind power represents the largest generating capacity among RES, being at the same time the most fluctuant. The capability to overcome the great disadvantage of wind power variability supports rising its penetration while preserving current operation modes of power systems, so new fashions to achieve this target are of great interest. This paper aims to prove the robustness of a recently introduced power management strategy, able to operate in online conditions, based on simultaneous perturbation stochastic approximation (SPSA) algorithm. To this regard, two different real datasets for wind power profiles with different statistical features are employed. The power management strategy is implemented on a hybrid energy storage system comprising a battery and a flywheel, modeled in Simulink/Matlab. The objectives of the proposed strategy are to reduce the instantaneous power ramp of the profile injected to the grid while smoothening the power profile exchanged by the battery in order to preserve it. Simulations are performed in representative conditions selected on statistical basis. It is demonstrated that the SPSA based power management achieves similar performances in all simulation conditions, proving to be robust. As a performance indicator, the reduction of the power ramp in reference to the 90% CDF threshold is evaluated. It is remarked as an 80% power ramp reduction is obtained towards the grid in both sites. Moreover, the further target is achieved in terms of battery lifetime extension; specifically, the fluctuation of the power profile exchanged by the battery is smoothed by 63% in the first site and 48% in the second, with respect to the flywheel one

Enzymatic Biofuel Cells: A Review on Flow Designs

Because of environmental concerns, there is a growing interest in new ways to produce green energy. Among the several studied applications, enzymatic biofuel cells can be considered as a promising solution to generate electricity from biological catalytic reactions. Indeed, enzymes show very good results as biocatalysts thanks to their excellent intrinsic properties, such as specificity toward substrate, high catalytic activity with low overvoltage for substrate conversion, mild operating conditions like ambient temperature and near-neutral pH. Furthermore, enzymes present low cost, renewability and biodegradability. The wide range of applications moves from miniaturized portable electronic equipment and sensors to integrated lab-on-chip power supplies, advanced in vivo diagnostic medical devices to wearable devices. Nevertheless, enzymatic biofuel cells show great concerns in terms of long-term stability and high power output nowadays, highlighting that this particular technology is still at early stage of development. The main aim of this review concerns the performance assessment of enzymatic biofuel cells based on flow designs, considered to be of great interest for powering biosensors and wearable devices. Different enzymatic flow cell designs are presented and analyzed highlighting the achieved performances in terms of power output and long-term stability and emphasizing new promising fabrication methods both for electrodes and cells

Development of a Decisional Procedure Based on Fuzzy Logic for the Energy Retrofitting of Buildings

This paper concerns the development of an automatic tool, based on Fuzzy Logic, which is able to identify the proper solutions for the energy retrofitting of existing buildings. Regarding winter heating, opaque and glazing surfaces are considered in order to reduce building heat dispersions. Starting from energy diagnosis, it is possible to formulate retrofitting proposals and to evaluate the effectiveness of the intervention considering several aspects (energy savings, costs, intervention typology). The innovation of this work is represented by the application of a fuzzy logic expert system to obtain an indication about the proper interventions for building energy retrofitting, providing as inputs only few parameters, with a strong reduction in time and effort with respect to the software tools and methodologies currently applied by experts. The novelty of the paper is the easy handling properties of the developed tool, which requires only a few data about the buildings: not many such methods were developed in the last years. The energy requirements for winter heating before and after particular interventions were evaluated for a consistent set of buildings in order to produce the required knowledge base for the tool’s development. The identified appropriate inputs and outputs, their domains of discretization, the membership functions associated to each fuzzy set, and the linguistic rules were deduced on the basis of the knowledge determined in this was. Therefore, the system was successfully validated with reference to further buildings characterized by different design and architecture features, showing a good agreement with the intervention opportunities evaluated